Fixed time interval line tracker control



Sept. 12, 1950 E.RATHJE 1 V 2,521,945

FIXED TIME INTERVAL LINE TRACKER CONTROL Filed Aug. 30, 1949 2 Sheets-Sheet 1 Rorafing Shu'Her/ 12 :22:5

1 10 Llghf Source I 6 'Norjh "'Amphfler '1 58 Temple? $0 36 {Shufier g 50 South 2 w Amplifier ii Puls e One Sho1' Machine Drive 14 Amplifier Muli'wlbrator Motors I 51 'Fixed'Time lnrerval"Con'rrol gfifi 24 4M 31 46 3] fi w 1 Am'gl ifier lNVENTOR EDWARD RATHJE ATTORNEY Sept. 12, 1950 E. RATHJE FIXED TIME INTERVAL LINE TRACKER CONTROL 2 Sheets-Sheet 2 Filed Aug. 30, 1949 z .owm .2: b KXKKK .Q Q .o M22 228 :Ees:

5&8 322 i INVENTOR EDWARD RATHJ E ATTORNEY Patented Sept. 12, 1950 FIXED TIME INTERVAL I E TRACKER W a CONTROL Edward Rathjc, Cranford, N."J'., assignor to The Linde Air Products Company, a corporation of Ohio Application August 30, 1949, Serial No. 113,168 I screens. (01. 250-a02) This invention relates toiline tracker controls for contourreproduotion of the type disclosed in Fowle wand Kennedy Patents"2,39'7,933 u and 2,430,924. a

In the Fowle and Kennedy system impulses from a photocell are directly transmitted to quadrature phase spaced power amplifier tubes in such a way that one correcting tube current changes ata greater rate than the opposite correcting tubecurrent, which adversely'affects' the sensitivity of the device. coupling. between the'photocell and the power amplifier tubes is not entirely 'stable. It also Another dis'ad-* vantage is that tracing is limited tothe'in'sideof 1 limits the amplification factor.

the templet, i. e., when light is appliedto the photocell.

verseefiect on the operation of the tracer.

The main object of this invention is to provide Kennedy patents. Other objects are to provide a line. tracker control which is'more sensitive, can I accommodate'a variety ofshutters with differ-" ent operating characteristics, is more stable, ca-

pable of greater amplification, can be adjusted for tracing either the inside or outside of the templet, eliminates the adverse effects of a nonuniiorm light pattern on the-operation of: the

tracer, and is simple and economical in itsparts.

Other objects will be clear to. those skilled in the art from the following description.

According to the invention there is provided a contour reproducing device having a linetra'cker control'including four amplifiers and a photo cell, provided with a fixed time interval control circuit coupling such photocell and the four amplifiers, including a pulse amplifier and a oneshot multivibrator, which improves the operation of the device by limiting the amount of time the photocell impulses are transmitted to the amplifier tubes. More specific features and additional advantages of the invention are set forth below.

In the drawings:

Fig. 1 is a plan view of a templet and pin-hole shutter illustrating the operation of the invention;

Fig. 2 is a simplified block-diagram of a fixed time interval line tracker control embodying the invention;

Figs. 3a-3d are time-space diagrammatic representations further illustrating the operation of the improved control system; and

Furthermore, the direct-.

Also a non-uniform light pattern at" every point around the tracing circle has an -adan improved line tracker control in a contour reproducer of the type disclosed in such Fowle and Figs. a-td are plan shutters which can be used with the new control.-

views As shown inFig. 2 a source of light: Ill, a rotating shutter i2 and a photocell Id are mounted in'a' tracing head so as to travel horizontally as a unit" with respect to "a stationary templet l6 which is disposed, for example, in a horizontal position between the light It and the shutter 12. The photocell id is coupled to quadrature phase spaced amplifiers i3, 29, 22 and 24 by a fixed time interval control circuit 26 comprising a pulse amplifier ZS'and a one-shot multivibrator 30. The amplifiers I8 and 26 are connected to a generator fifi which energizes a north-south motor 38. The

amplifiers 22 and 2d are connected to a generator 44 which energizes an east-west motor 45.

The motors 38 and 46 drive the machine (not shown) which carries the unit containing light shutter 52 rotates at synchronous speed as in the patented method and thus provides means for timing the operation of the four amplifiers Referring toFigure 30; when the shutter IZro tates to the position shown, light fallsthrough pin-hole 25 upon the phototube It, and a voltage' pulse 48 is developed across a'load'resistor 50 connected in series with the phototube by a switch 5 suchresistor is capacitlvely coupled at 52 to the pulse amplifier -28 which amplifies the pulse without changing the timing. The amplified pulse is used to trigger the one-shot multivi This is a well known" component (see brator 30. page 277, Industrial Electronics Reference Book) which gives a pulse output 56 of a fixed time duration, the beginning of such pulse 56 coinciding with the trigger pulse 54.

The square wave output 56 of the multivibrator St is applied to the grids of the four amplifier tubes 3-24, and from there the operation of the system is the same as thatof the Fowle and Kennedy patents. With the timing shown in Figure 3a, the West tube 24 gives maximum output W, the North and South tubes I8 and 20 gives one half maximum output N and S which balances out in the North-South generator 38. The resultant motion of the machine is'in the West direction.

Figure 3b shows how a correcting motion is obtained when the templet I6 is too far over the tracing head. In this case light hits the phototube l4 some 45 degrees later and the square ,ENT f QLF of several dififerent obtained when the contour of the templet.

changes.

The sensitivity of the tracer can be varied by varying the radius R (Fig. 1) of the pin-hole 25, and the efiective tracing radius r can be varied by changing the timing of the. shutter by shifting I the stator of the shutter driving motor a fraction of a revolution in either direction The operation of the present control system is not limited to use with a simple pin-hole shutter H. In fact better control of the sensitivity and the tracing radius can be obtained by using a shutter 60 (Fig. 4b) with a series of pin-holes 61-65 at varying radii from the center of the shutter. Other modifications are the eccentric arcuate slot 66, and eccentric semi-circular opening 58 (Figs. 4c and 411) which are very successful.

Some of the advantages of the present improved control are: increased sensitivity of the system, because one correcting tube current is increased whil the opposite correcting tube current is decreased, whereas with the Fowle and Kennedy system one correcting tube current is increased or decreased at a greater rate than the other. Any one of a variety of types of shutters can be used, each with difierent operating characteristics. The A.-C. coupling between the phototube and the power tubes is much more stable and capable of greater amplification than a direct-coupling between the phototube and the power amplifier tubes. inside or the outside of the templet for cutting male and female mating pieces is possible and can be accomplished by simply adjusting switch 5! so that the system can use either the pulse when light strikes the phototube, or the other (dark) pulse when light is cut off thephototube.

The efiects of a non-uniform light pattern on the operation of the tracer are eliminated. As long Tracing on either the as there is sufiicient light at every point around the tracing circle to trigger the multivibrator 30, any light variations above this minimum value will have no effect upon the timing of the four a power output tubes.

What is claimed is:

1. In a line tracker control system comprising a photocell and quadrature phase spaced power amplifier tubes for reproducing contours, a fixed time interval control circuit comprising a pulse amplifier and a one-shot multivibrator coupled to said amplifien: said, circuit connected between such photocell and the quadrature phase spaced power amplifier tubes and acting to limit the amount of time each photocell impulse is transmitted to said amplifier tubes.

2. In a line tracker control, the combination with a. phototube and quadrature phase spaced power amplifiers, '01 a time interval control circuit coupling said phototube to said amplifiers for the purpose of improving the operation of the control by limiting the amount of time each impulse from the phototube is transmitted to the power amplifier tubes.

3. In a contour reproducer comprising a line tracker control including quadrature phase spaced power amplifiers and a tracing head in-. cluding a photocell responsive to light impulses transmitted through a shutter which rotates at a fixed speed, a fixed time interval control circuit comprising an impulse amplifier operatively as; sociated with said photocell, and a one-shot mu];

tivibrator operatively associated with said impulse amplifier and said power amplifiers which applies: an impulse of fixed duration to said power amplifiers in response. to each triggering impulse from said photocell occurring when saidmulti-l vibrator isnot. applying an impulse to the power" amplifiers, whereby the operation of the contour I reproduceris stabilized.

4. In a line tracker control system comprisin quadrature phase spaced power amplifiers and a photocell for reproducing contours, a pulse amplifier, an alternating current coupling connect, ing said pulse amplifier to said photocell, and a multivibrator connected to said pulse amplifier and tosa-id power amplifiers.

5. In a line tracker control system, as defined by claim 4, means for switching said photocell 'forresponse of thesystem to either light or dark impulses on the photocell;

, EDWARD RA'IHJE.

R RENC S C TED The following references are of record in the Name Date F wlc et a1. "fit-i" Ap 1 Number Fowle et al. Nov. 18, 19,4! 

